1. Field of the Invention
The present invention relates to a toner fixing apparatus for a wet-type electrophotographic printing device using a developing liquid composed of a liquid toner and a carrier liquid, and to an electrophotographic printing device provided with the toner fixing apparatus. The present application claims priority from Japanese Patent Application No. 2008-258818, filed Oct. 3, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
In an imaging system using a developing liquid composed of a liquid toner (hereafter “toner”) and a carrier liquid, the carrier liquid is absorbed by paper when transferring a toner image transcribed onto an intermediate transfer body onto the paper. When the paper passes through a plurality of units provided with an intermediate transfer body to form a multicolored image, the paper contains several color components and a large amount of carrier liquid (for example refer to Japanese Patent Application Laid-Open No. 2007-11142). Consequently a large amount of carrier liquid must be dried and removed from the paper in order to fix the toner. A conventional heated roller method is known as a technique of fixing toner by drying and removing carrier liquid absorbed by paper. However this method has limitations resulting from the contact time and the contact temperature with the printed surface. In view of the above, a non-contact hot-air fixing apparatus has been proposed (for example, refer to Japanese Utility Model Application Laid-Open No. 2-51353). According to this hot-air fixing device, it is possible to ensure the maintenance of a long contact time of hot air with the paper easily by forming the fixing device along the length of the displacement route of the paper. In addition, according to this hot-air fixing device, it is possible to increase the contact temperature of the hot-air with the paper by increasing the hot-air temperature.
However, the non-contact hot-air fixing device above-mentioned has the following problems.
(a) The above-mentioned non-contact hot-air fixing device places the heated air in contact with the paper by discharging heated air from a plurality of through holes provided in a plate-shaped heater body. However an increase in the contact area of the heated air for the paper and elongation of the device to ensure contact time has an adverse effect on the performance of air discharge from through holes in proximity to a central portion of the heated air blow region (region connected with the heater body). Thereby, the heating efficiency is reduced due to the absence of heated air circulation and contamination results from delay of vapor components in residual toner.
(b) When the temperature of heated air is increased to improve fixing properties, stretching or creasing of the paper results from excess heat and affects paper transfer.
(c) The length of the fixing apparatus is increased proportional to the number of colors and results in an increase in the overall size of the apparatus and consequently causes problems associated with installation space.